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1. DM and HCP
Early Detection of Heat and Cold
Perception in Diabetic Neuropathy
Issues and Reasons
Dhananjay Kelkar
Dhansai Laboratory, Mumbai

2. Anatomy of Heat, Cold
and Pain Perception
 Small Fibers sub-serve warm cold and
pain sensation – The C fibers
 C Fibers – Unmyelinated, without
specialized Nerve endings, lying naked
in tissues
 Distinct from A delta – deep aches and
pain

3. Symptoms 1
 Diabetic foot ulcers has great impact on
morbidity and mortality of life
 First symptoms to appear – pain,
hyperesthesia, hyperalgesia, allodynia -
that is contact pain
 Abnormalities of C fibers supposedly
responsible for early occurrence of
symptoms

4. Symptoms 2
Other somatic sensations of pressure, touch,
vibration, proprioception are likely as not, not
affected at this stage
 Makes more sense to detect HC thresholds
 Early pain and heat hyperalgesia and later
hypoalgesia>Further damage to C fibers
 Also impairs the warm thermal perceptions
(Aron Vinik – Exp Clin Endocrinol Diabetes-
109 (2001) (Suppl 2)

5. Time of Damage
 Other authors have also considered
these to be the first fibers to be affected
in diabetic neuropathy
(Jamal et al, 1987, Dyck, 1988, Hanson
et al, 1992, as quoted by Vinik vide
above)
 Various symptoms occur when there is
on going damage to the nerves initially

6. Time and Sequence of Damage
 Pain of A delta – thinly myelinated is
deep seated and gnawing,
 Pain of C fibers is described in most
vivid terms like burning, bursting,
walking on hot pebbles and sand etc
 Symptoms occur when structural
damage has occurred - not without it

7. Some More Concerns
 Diabetes affects rhythmic vasomotion of small
arterioles due to sympathetic damage early in
disease,
 Loss of warm thermal threshold also occurs
early with C fiber damage and correlates
significantly to reduced vasomotion
(Vinik – ibid)
 Exact cause effect or association between
vasomotion and C fiber damage as a time
relationship is not established (ibid)

8. Pathological Evidence
 Skin biopsies in persons with Diabetes
show – uniform depletion of substance
P, CGRP and the cytoplasmic proteins
PGP 9.5 for small fiber specificity
(Levy et al, 1992,Wallargren et al, 1995, Lauria et al,
1998,and others)
 Glabrous skin of the foot is far more
affected by Diabetes than that of hand

9. Can we do something?
 Detect early?
 Of what use?
 Cost effective?
 Other benefits?
 Can we stop progression?
 Can we reverse abnormalities?
 Is detection easy?

10. Can we do something? - 2
 Can we stop progression?
 Can we reverse abnormalities?
 Enough medical evidence to say
yes to these questions – if the
detection is early enough
 Malady is – failure of early
detection

11. Can we do something?- 3
 Detect early?
 Yes. Sensitive and simple instrument for
detection, detects heat, cold, heat pain and
cold pain thresholds,
 Used by many – Further simplified on
feedback after field study
 Reliable and reproducible thresholds
 Needs grasp of the working of the instrument

12. Can we do something? - 4
 Cost effective?
 Needs time, about 15 to 20 minutes of
technician, Used carefully – no
maintenance cost, after sales service,
no consumables required etc;

13. Can we do something? - 5
 Other benefits?
 Indicates simultaneous
possibility of Autonomic
dysfunction
 Acts as motivator for better
glucose control

14. Tissue Damage
 Heat pain threshold range is 42
to 45 0
C
 Erythema takes place after an
hour at 45 0
C
 Needs 10 second to a minute at
50 0
C
 And just One second at 55 0
C

15. A Little Physiology - 1
 C fibers carry sensations slower, have a
period of latency of about 500
milliseconds before the impulse gets
initiated
 Consequently there is a further delay in
reaching the sensation to the cortical
areas as the velocities are slow,
therefore
 There is a further delay for the
registration of the sensation and
response to it

16. A Little Physiology - 2
 These factors dictate the working of he
instrument
 These factors determine the rise of
temperature in degrees as well as the
time taken to change the level of
temperature
 Applies also to the rate of fall of
temperature in time

17. A Little Physiology - 3
 A rate of one degree per second is
generally recommended
 For heat and cold thresholds the rate of
rise or fall of temperature seems best at
1 degree Celsius over 4 seconds
 This makes testing a little longer but
gives precise thresholds, reduces the
need for many readings, averaging etc

18. Needed
 Early detection
 Early detection of the early
fibers that are affected
 HCP is an answer

19. Sensitometer-HCP Made in
India

20. HCP Probe

21. A Little Physiology - 4
 Concept of heat pain and cold pain should be
understood; these thresholds are higher and
lower than heat and cold respectively
 Cool pain is sensation of coolness with an
additional component of un-comfort
 Heat pain is warmth plus pricking sensation
 It is the slight un-comfort and not, not the
ability to bear

22. A Little Physiology - 5
 The rate of rise or fall of temperature to
detect Heat pain & Cool Pain also
seems best at 1 degree Celsius over 4
seconds
 Two additional thresholds make testing
a little longer but gives precise
thresholds,
 Only cool and heat pain thresholds are
enough for clinical practice

23. Operation of the instrument 1

24. Operation of the instrument 2

25. Normal range
 32 to 34 o
C is neutral zone
 Just bellow 32 o
C & up to 30 o
C is the Cool
threshold range -age dependant
 27 to 25 o
C Cool pain
 36 to 38 o
C warm
 And 42 to 45 o
C Heat pain zone
 Above ranges are true for clinical practice in
an ambiant temperature of 27 to 37 o
C

26. Other featchers
 It can be operated through PC
 Report can be generated through PC
 Data can be stored and retrieved for
future use
 Data can be picked by hospital/clinic
management system as well

27. Thank you for a
patient hearing